This invention relates to methods and apparatus for determining the ash content in ash-containing slurries. In one aspect, the invention relates to methods and apparatus for making an on-line measurement of the ash content of coal in an aqueous slurry.
Because of the low price of coal in the past, only very simple and inexpensive processing methods were employed to reduce the content of ash-forming inorganic materials prior to burning. The price of coal is now several times what it was ten years ago and more sophisticated coal-cleaning processes now are cost justified. The productivity and/or product quality of such cleaning processes depends to a large extent on process control. An important part of an effective process control is the capability of continuously monitoring the ash content of a coal so that process conditions can be changed in response to changes in the composition of the coal entering a plant. Such a capability is also useful in process control for other applications, such as coal liquification and gasification and coal-water fuel production.
The most widely used methods and devices for measuring the ash content of coal employ either x-ray fluorescence analysis or a comparison of Compton and Rayleigh intensities. Representative prior art devices are disclosed in the following patents:
______________________________________ Patents U.S. Pat. No. Issue Date ______________________________________ Rhodes 3,270,204 August 20, 1966 Lubecki et al. 4,388,530 June 14, 1983 Lubecki et al. 4,450,576 May 22, 1984 Page et al. 4,486,894 December 4, 1984 Watt et al. 4,566,114 January 21, 1986 ______________________________________
Such prior devices typically are quite expensive and/or imprecise.